Spraying apparatus and method



May 11, 1965 J. o. TRIMBLE SPRAYING APPARATUS AND METHOD COOLANT SUPPLY POWER SUPPLY SUPPLY METAL Filed Feb. 8, 1961 AIR SUPPLY FICT-i mm T m L V Y M 0 1m T A TTORNE Y United States Patent 3,182,361 SPRAYING APPARATUS AND METHOD John 0. Trimble, Malvern, Pan, assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Feb. 8, 1961, Ser. No. 87,810 4 Claims. (Cl. 22-193) This invention relates to metal spraying apparatus, and more particularly to an apparatus for controlling the heat build-up encountered when spraying molten metals.

Usually molten metals are sprayed on various materials for the purpose of bonding a metal layer to the material being sprayed. Thin layers of molten spray may be deposited in such small isolated amounts that it does not cause appreciable distortion of the material when the spray metal shrinks upon cooling, but this method is not acceptable for precision work or the deposit of large amounts of metal.

Molten metals are sprayed on various materials for the purpose of producing a negative shell impression of the surface of the material. Formerly there was no acceptable way of avoiding the distortions of shrinkage due to cooling of large masses of metal. Normalizing has been used to diminish, but not cure, such distortions in shells created by spray metals.

It would be desirable if metal could be sprayed from the molten state upon a pattern to produce an exact negative impression free from shrinkage and distortions.

It is therefore a general objection to provide an apparatus and method for obtaining a non-distorted metal negative from a pattern.

It is a further object to provide means for spraying molten metal upon an object without heating the object being sprayed.

It is another object to provide a method of producing a porous spray metal negative shell from a pattern.

In accordance with the invention there is provided an apparatus for spraying pre-molten metal in a porous layer on a surface, comprising in combination a preheated spray gun device for spraying the pre-molten metal on a surface and an adjustable nozzle mounted on a bracket outboard of either side of said spray gun device for simultaneously spraying a chilled gaseous cooling substance on the surface adjacent the molten spray.

Other features and objects of the invention will be found throughout the more detailed description of the invention which follows. These novel features believed descriptive of the nature of the invention are described with particularity in the appended claims. To more clearly portray the invention and its manner of operation the description is supplemented with the accompanying drawings:

FIG. 1 is a schematic view of a preferred spray device equipped with cooling nozzles for practicing the invention with the novel apparatus shown in perspective view. The supply lines and controls for the spray device are shown diagrammatically.

FIG. 2 is a top view of the spray nozzles.

Referring now more particularly to the drawing, there is illustrated a metal spray gun device It which has a thermostatically controlled heating head 12. Thermocouple devices 14 imbedded in the head 12 with the resistance heaters, not shown, cooperating with control T maintain the metal in the gun in a molten state. The gun 10 illustrated is designed to spray metal contained in a large reservoir 16 by means of preheated air and permits continuous operation. A conduit 18 connected to the reservoir 16 and to the gun 10 is heated by a resistance heater 20 which is thermostatically controlled by control T cooperating with a thermocouple device 22 imbedded inside the insulation cover 24.

A bracket 26 is mounted on the gun device 10 having outward extending lateral portions with apertures therein. Conduits 28 containing a cooling substance connect to the coolant supply 30 and the nozzles 32 at the apertures in the bracket 26 by well known fittings. The amount of coolant is regulated by a flow regulation device 34 connected in the conduit 28. Nozzles 32 and conduit 28 are preferably insulated to avoid surface condensation. Nozzles 32 are preferably constructed of a flexible material to allow for directional flow, or have spray adjustment heads. Several nozzles 32 may be provided as to surround the metal spray 36 to speed the operation of cooling the spray metal as it is deposited.

In operation, the above-described apparatus is employed to spray a jet of molten metal 36 such as zinc, tin or lead onto a pattern 38 made of wood, metal, plastic or plaster while maintaining cooling jets 40 of CO or liquefied gas directed adjacent the molten spray 36.

When the temperature of the molten metal is held slightly above its melting point and the pattern to be sprayed is held near room temperature a fine spray of molten metal may be directed onto a pattern 38 so as to cause the molten metal spray drops to slightly splatter or flatten as they adhere firmly to the pattern. This produces a smooth exact negative duplicate shell of the pattern being sprayed which has porous qualities. Should additional molten metal be deposited in the same area without the benefit of the coolant substance the pattern begins a process of thermal expansion and the metal deposited on the pattern begins to heat up causing blisters and loss of adhesion as well as an independent process of thermal expansion. If the metal deposited builds up too much heat the subsequently deposited molten metal no longer forms a porous shell but forms a non-porous continuous-cast shell over the pattern. In order to prevent any thermal distortions of the pattern or the shell being produced by the molten spray the nozzles 32 are adjusted by flow regulation device 34 to maintain the spray metal shell at approximately room temperature. This is to say that the molten metal is deposited in a molten state on the pattern and is cooled after being deposited down to the temperature of the pattern, thus establishing the pattern and the shell at an equilibrium temperature approximating room temperature. The correct adjustment for the apparatus is easily obtained by directing the coolant substance adjacent the cone of the metal spray so as to cool the deposited material shortly after it has been sprayed. The gun device 10 is preferably moved in a line with the cooling jet so that the deposited molten metal is isolated and cooled.

As is well known in the casting art the higher the temperature of the metal deposited the greater the amount of shrinkage encountered. This rule is not applicable to the present method for as each isolated spot of metal is deposited it is immediately cooled to approximately room temperature. The resulting shell is eifect-ively deposited at room temperature with no shrinkage. Spray metal may be deposited at a range of temperatures in the molten stated. As the temperature of the metal is increased it becomes more difiiicult to get the spray met-a1 to stick to the pattern, but it is sometimes desirable to spray at elevated temperatures for the shell so formed is more dense. It has been found that the novel apparatus allows spray metal to be deposited on the pattern with superior adhesion qualities even though at elevated temperatures. The apparatus permits the metal to be spnayed at elevated temperatures and chilled to a point Where it is barely molten as it adheres to the pattern. Such flexibility permits the spray shell to be formed practically like a homogeneous casting or to the other extreme where the molten metal is very porous without depending on the critical control of the metal supply temperature.

aneaeer Negative impressions of patterns made by the novel apparatus andmethod are preferably slightly porous, extremely smooth and dimensionally accurate reproductions of the patterns and-are free from thermal distortions.

it is to be understood that the form of the invention shown is only illustrative of the invention, and that various changes and modifications in the apparatus may be made without departing from the scope of my invention; some of the novel features of which are defined in the appended claims.

What is claimed is z;

1. In an improved method of producing molds by spraying a plurality of layers of molten metal on a pattern and removing the built-up layers as a metal mold, the steps comprising,

heating a mass of low temperature metal to a molten state barely above its melting temperature; I

spraying a jet of the pre'mol'ten metal on a small area portion of the pattern;

spraying simultaneously a jet of liquified gas coolant apart from and adjacent to said jet of pre-molten metal;

simultaneously moving said jets so that the jet of mol- .ten metal is deposited on the pattern and the jet of liquified gas coolant impinges on the just deposited molten metal, sufficiently cooling the deposited metal to the temperature of the pattern to avoid heating the pattern; 7

building up a spray metal mold as a plurality of layers on the pattern by continuously spraying the jet of pre-rnolten metal on the pattern and simultaneously cooling the just deposited metal to the temperature of the pattern;

and removing from the pattern a shrink-free and distorti-on free spray metal mold.

2. In an improved method of producing molds by spraying a plurality of layers of metal on a pattern and removing the built-up layers as a metal mold from the pattern, the steps of;

spraying a jet of pro-molten metal on the pattern in molten form;

simultaneously spraying a jet of liquified gas coolant on the pattern adjacent the jet of pre-rnolten metal in a manner which avoids contact of the jet of coolant with the jet of pro-molten metal in transit to the pattern;

simultaneously movingthe jet of coolant and jet of molten metal so that the jet of coolant impinges on the just deposited of molten metal to immediately cool the molten metal spray just deposited to the temperature of the pat-tern to prevent the molten deposit from heating the pattern;

and repeain-g the spraying and cooling steps so that a plurality of layers of spray metal is built up on the pattern, each layer being cooled before a subsequent layer is deposited so that neither the pattern nor the layers previously deposited are heated by the molten metal spray.

3. A spray gun apparatus for spraying pro-melted molten metal on an object and instantaneously cooling the deposited molten metal sufiiciently to prevent any heat build-up in the object being sprayed comprising:

(a) a movable heated spray gun having a spray nozzle therein for spraying molten metal;

(b) a stationary heated reservoir of pre-rnolten metal;

(c) a heated flexible conduit connecting said spray nozzle to said stationary reservoir;

(d) aspiration jets in said gun adjacent said nozzle tor propelling a spray of said pre-molten metal from said spray nozzle;

.(e) an insulating bracket mounted on said spray gun and extending outward therefrom;

l (f) and cooling jet means mounted on said insulating bracket remote from said heated spray gun; (g) said jet means comprising:

(1) a source of liquified gas, ('2) connected by flexible connections, to (3) a tubular jet pipe mounted on and extending outward from said insulating bracket and said gun and terminating adjacent the path of said spray of said molten metal and providing a spray of expanding cold gas-at a point adjacent the path of said spray of molten metal on the object being sprayed, whereby the molten metal being sprayed is deposited on theobject being sprayed in molten form and instantaneously V cooled by said cooling jet means to the temperature of the object being sprayed preventing heat transfer between the sprayed metal and the object.

4. An apparatus for spraying pre-melted molten metal on an object and simultaneously cooling said sprayed molten metal to prevent heating of the object being sprayed, V

(a) a stationary reservoir of pre-melted molten metal,

(15) a movable heated-head-gun, 7

(c) a spray nozzle in said movable heated-head-gun,

(d) a flexible heated conduit connecting said stationary reservoir of pre-melted molten metal to said spray nozzle in said movable beated-head-gun for supplying said pre-melted molten metal to said nozzle without heating or cooling said metal, 7

(e) jet spray means in said heated-head-gun adjacent said spray nozzle for releasing and iatomizing said supply of pre-rnelted molten metal from said nozzle to provide a spray of molten metal without increasing the temperature of said pre-melted molten-metal in the nozzle,

(f) an insulating bracket mounted on said heated head- (g) .jet cooling means mounted on said insulating bracket at a point removed from said heated-beadgun so as to prevent cooling said spray nozzle in said heated-head-gun,

(h) said jet cooling means including an elongated tubular nozzle extending outward from said braclret and said heated-head-gun in the direction of said spray of molten metal and terminating at a point spaced from the path of said spray of molten metal and terminated to direct a stream of coolant onto the object to be sprayed at a point spaced alongside said path of said spray of molten metal thereby permitting concentrated streams of gas coolants to be sprayed adjacent to and simultaneously with said spray metal in sufiicient quantities to remove all the heat supplied said object by said spray metal without affecting the temperature ofthe spray of molten metal in transit.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 6/09 France. 4/58 Canada.

RICHARD D. NEVIUS, Primary Examiner.

I JOSEPH REBOLD, Examiners.

Sullivan et al 118-69 

1. IN AN IMPROVED METHOD OF PRODUCING MOLDS BY SPRAYING A PLURALITY OF LAYERS OF MOLTEN METAL ON A PATTERN AND REMOVING THE BUILT-UP LAYERS AS A METAL MOLD, THE STEPS COMPRISING, HEATING A MASS OF LOW TEMPERATURE METAL TO A MOLTEN STATE BARELY ABOVE ITS MELTING TEMPERATURE; SPRAYING A JET OF THE PRE-MOLTEN METAL ON A SMALL AREA PORTION OF THE PATTERN; SPRAYING SIMULTANEOUSLY A JET OF LIQUIFIED GAS COOLANT APART FROM THE ADJACENT TO SAID JET OF PRE-MOLTEN METAL; SIMULTANEOUSLY MOVING SAID JETS SO THAT THE JET OF MOLTEN METAL IS DEPOSITED ON THE PATTERN AND THE JET OF LIQUIFIED GAS COOLANT IMPINGES ON THE JUST DEPOSITED MOLTEN METAL, SUFFICIENTLY COOLING THE DEPOSITED METAL TO THE TEMPERATURE OF THE PATTERN TO AVOID HEATING THE PATTERN; AND REMOVING THE PATTERN A SHRINK-FREE AND DISTORTION-FREE SPRAY METAL MOLD. 